Overt vs. covert speed cameras in combination with delayed vs. immediate feedback to the offender

  • Published: Accident Analysis and Prevention, Volume 79, 2015
  • Authors: H. Marciano, P. Setter, J.Norman
  • Date Added: 11 Feb 2016
  • Last Update: 11 Feb 2016
  • Format: html


To reach the optimal enforcement design for speed cameras


A simulator study tested speed camera concealment and fine timing

Key Findings:

  • Most of the world’s speed cameras are covert but there is some evidence that this can cause a ‘kangaroo effect’ in driving patterns. One suggested alternative to prevent this kangaroo effect is the use of covert cameras. Another issue relevant to the effect of enforcement countermeasures on speeding is the timing of the fine. There is general agreement on the importance of the immediacy of the punishment, however, in the context of speed limit enforcement, implementing such immediate punishment is difficult. An immediate feedback that mediates the delay between the speed violation and getting a ticket is one possible solution.

  • This study examines combinations of concealment and the timing of the fine in operating speed cameras in order to evaluate the most effective one in terms of enforcing speed limits.

  • Using a driving simulator, the driving performance of the following four experimental groups was tested: (1) overt cameras with delayed feedback; (2) overt cameras with immediate feedback; (3) covert cameras with delayed feedback; and (4) covert cameras with immediate feedback. Each of the 58 participants drove in the same scenario on the three different days.

  • The results showed that both median speed and speed variance were higher with overt than with covert cameras. Moreover, implementing a covert camera system along with immediate feedback was more conducive to drivers maintaining steady speeds at the permitted levels from the very beginning.

  • Both ‘overt cameras’ groups exhibit a kangaroo effect throughout the entire experiment.

  • It can be concluded that an implementation strategy consisting of covert speed cameras combined with immediate feedback to the offender is potentially an optimal way to motivate drivers to maintain speeds at the speed limit.


Strong experimental design assessing the impact of different combinations of enforcement strategy.